// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

/*============================================================
**
**
**
** Purpose: A wrapper class for the primitive type float.
**
**
===========================================================*/

using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;

using Internal.Runtime.CompilerServices;

namespace System
{
    [Serializable]
    [StructLayout(LayoutKind.Sequential)]
    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
    public readonly struct Single : IComparable, IConvertible, IFormattable, IComparable<float>, IEquatable<float>, ISpanFormattable
    {
        private readonly float m_value; // Do not rename (binary serialization)

        //
        // Public constants
        //
        public const float MinValue = (float)-3.40282346638528859e+38;
        public const float Epsilon = (float)1.4e-45;
        public const float MaxValue = (float)3.40282346638528859e+38;
        public const float PositiveInfinity = (float)1.0 / (float)0.0;
        public const float NegativeInfinity = (float)-1.0 / (float)0.0;
        public const float NaN = (float)0.0 / (float)0.0;

        // We use this explicit definition to avoid the confusion between 0.0 and -0.0.
        internal const float NegativeZero = (float)-0.0;

        //
        // Constants for manipulating the private bit-representation
        //

        internal const uint SignMask = 0x8000_0000;
        internal const int SignShift = 31;
        internal const int ShiftedSignMask = (int)(SignMask >> SignShift);

        internal const uint ExponentMask = 0x7F80_0000;
        internal const int ExponentShift = 23;
        internal const int ShiftedExponentMask = (int)(ExponentMask >> ExponentShift);

        internal const uint SignificandMask = 0x007F_FFFF;

        internal const byte MinSign = 0;
        internal const byte MaxSign = 1;

        internal const byte MinExponent = 0x00;
        internal const byte MaxExponent = 0xFF;

        internal const uint MinSignificand = 0x0000_0000;
        internal const uint MaxSignificand = 0x007F_FFFF;

        /// <summary>Determines whether the specified value is finite (zero, subnormal, or normal).</summary>
        [NonVersionable]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool IsFinite(float f)
        {
            int bits = BitConverter.SingleToInt32Bits(f);
            return (bits & 0x7FFFFFFF) < 0x7F800000;
        }

        /// <summary>Determines whether the specified value is infinite.</summary>
        [NonVersionable]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static unsafe bool IsInfinity(float f)
        {
            int bits = BitConverter.SingleToInt32Bits(f);
            return (bits & 0x7FFFFFFF) == 0x7F800000;
        }

        /// <summary>Determines whether the specified value is NaN.</summary>
        [NonVersionable]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static unsafe bool IsNaN(float f)
        {
            // A NaN will never equal itself so this is an
            // easy and efficient way to check for NaN.

            #pragma warning disable CS1718
            return f != f;
            #pragma warning restore CS1718
        }

        /// <summary>Determines whether the specified value is negative.</summary>
        [NonVersionable]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static unsafe bool IsNegative(float f)
        {
            return BitConverter.SingleToInt32Bits(f) < 0;
        }

        /// <summary>Determines whether the specified value is negative infinity.</summary>
        [NonVersionable]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static unsafe bool IsNegativeInfinity(float f)
        {
            return f == float.NegativeInfinity;
        }

        /// <summary>Determines whether the specified value is normal.</summary>
        [NonVersionable]
        // This is probably not worth inlining, it has branches and should be rarely called
        public static unsafe bool IsNormal(float f)
        {
            int bits = BitConverter.SingleToInt32Bits(f);
            bits &= 0x7FFFFFFF;
            return (bits < 0x7F800000) && (bits != 0) && ((bits & 0x7F800000) != 0);
        }

        /// <summary>Determines whether the specified value is positive infinity.</summary>
        [NonVersionable]
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static unsafe bool IsPositiveInfinity(float f)
        {
            return f == float.PositiveInfinity;
        }

        /// <summary>Determines whether the specified value is subnormal.</summary>
        [NonVersionable]
        // This is probably not worth inlining, it has branches and should be rarely called
        public static unsafe bool IsSubnormal(float f)
        {
            int bits = BitConverter.SingleToInt32Bits(f);
            bits &= 0x7FFFFFFF;
            return (bits < 0x7F800000) && (bits != 0) && ((bits & 0x7F800000) == 0);
        }

        internal static int ExtractExponentFromBits(uint bits)
        {
            return (int)(bits >> ExponentShift) & ShiftedExponentMask;
        }

        internal static uint ExtractSignificandFromBits(uint bits)
        {
            return bits & SignificandMask;
        }

        // Compares this object to another object, returning an integer that
        // indicates the relationship.
        // Returns a value less than zero if this  object
        // null is considered to be less than any instance.
        // If object is not of type Single, this method throws an ArgumentException.
        //
        public int CompareTo(object? value)
        {
            if (value == null)
            {
                return 1;
            }

            if (value is float f)
            {
                if (m_value < f) return -1;
                if (m_value > f) return 1;
                if (m_value == f) return 0;

                // At least one of the values is NaN.
                if (IsNaN(m_value))
                    return IsNaN(f) ? 0 : -1;
                else // f is NaN.
                    return 1;
            }

            throw new ArgumentException(SR.Arg_MustBeSingle);
        }

        public int CompareTo(float value)
        {
            if (m_value < value) return -1;
            if (m_value > value) return 1;
            if (m_value == value) return 0;

            // At least one of the values is NaN.
            if (IsNaN(m_value))
                return IsNaN(value) ? 0 : -1;
            else // f is NaN.
                return 1;
        }

        [NonVersionable]
        public static bool operator ==(float left, float right) => left == right;

        [NonVersionable]
        public static bool operator !=(float left, float right) => left != right;

        [NonVersionable]
        public static bool operator <(float left, float right) => left < right;

        [NonVersionable]
        public static bool operator >(float left, float right) => left > right;

        [NonVersionable]
        public static bool operator <=(float left, float right) => left <= right;

        [NonVersionable]
        public static bool operator >=(float left, float right) => left >= right;

        public override bool Equals(object? obj)
        {
            if (!(obj is float))
            {
                return false;
            }
            float temp = ((float)obj).m_value;
            if (temp == m_value)
            {
                return true;
            }

            return IsNaN(temp) && IsNaN(m_value);
        }

        public bool Equals(float obj)
        {
            if (obj == m_value)
            {
                return true;
            }

            return IsNaN(obj) && IsNaN(m_value);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override int GetHashCode()
        {
            int bits = Unsafe.As<float, int>(ref Unsafe.AsRef(in m_value));

            // Optimized check for IsNan() || IsZero()
            if (((bits - 1) & 0x7FFFFFFF) >= 0x7F800000)
            {
                // Ensure that all NaNs and both zeros have the same hash code
                bits &= 0x7F800000;
            }

            return bits;
        }

        public override string ToString()
        {
            return Number.FormatSingle(m_value, null, NumberFormatInfo.CurrentInfo);
        }

        public string ToString(IFormatProvider? provider)
        {
            return Number.FormatSingle(m_value, null, NumberFormatInfo.GetInstance(provider));
        }

        public string ToString(string? format)
        {
            return Number.FormatSingle(m_value, format, NumberFormatInfo.CurrentInfo);
        }

        public string ToString(string? format, IFormatProvider? provider)
        {
            return Number.FormatSingle(m_value, format, NumberFormatInfo.GetInstance(provider));
        }

        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null)
        {
            return Number.TryFormatSingle(m_value, format, NumberFormatInfo.GetInstance(provider), destination, out charsWritten);
        }

        // Parses a float from a String in the given style.  If
        // a NumberFormatInfo isn't specified, the current culture's
        // NumberFormatInfo is assumed.
        //
        // This method will not throw an OverflowException, but will return
        // PositiveInfinity or NegativeInfinity for a number that is too
        // large or too small.
        //
        public static float Parse(string s)
        {
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Number.ParseSingle(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo);
        }

        public static float Parse(string s, NumberStyles style)
        {
            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Number.ParseSingle(s, style, NumberFormatInfo.CurrentInfo);
        }

        public static float Parse(string s, IFormatProvider? provider)
        {
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Number.ParseSingle(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.GetInstance(provider));
        }

        public static float Parse(string s, NumberStyles style, IFormatProvider? provider)
        {
            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
            return Number.ParseSingle(s, style, NumberFormatInfo.GetInstance(provider));
        }

        public static float Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Float | NumberStyles.AllowThousands, IFormatProvider? provider = null)
        {
            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
            return Number.ParseSingle(s, style, NumberFormatInfo.GetInstance(provider));
        }

        public static bool TryParse([NotNullWhen(true)] string? s, out float result)
        {
            if (s == null)
            {
                result = 0;
                return false;
            }

            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo, out result);
        }

        public static bool TryParse(ReadOnlySpan<char> s, out float result)
        {
            return TryParse(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo, out result);
        }

        public static bool TryParse([NotNullWhen(true)] string? s, NumberStyles style, IFormatProvider? provider, out float result)
        {
            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);

            if (s == null)
            {
                result = 0;
                return false;
            }

            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
        }

        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider? provider, out float result)
        {
            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
        }

        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out float result)
        {
            return Number.TryParseSingle(s, style, info, out result);
        }

        //
        // IConvertible implementation
        //

        public TypeCode GetTypeCode()
        {
            return TypeCode.Single;
        }

        bool IConvertible.ToBoolean(IFormatProvider? provider)
        {
            return Convert.ToBoolean(m_value);
        }

        char IConvertible.ToChar(IFormatProvider? provider)
        {
            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Single", "Char"));
        }

        sbyte IConvertible.ToSByte(IFormatProvider? provider)
        {
            return Convert.ToSByte(m_value);
        }

        byte IConvertible.ToByte(IFormatProvider? provider)
        {
            return Convert.ToByte(m_value);
        }

        short IConvertible.ToInt16(IFormatProvider? provider)
        {
            return Convert.ToInt16(m_value);
        }

        ushort IConvertible.ToUInt16(IFormatProvider? provider)
        {
            return Convert.ToUInt16(m_value);
        }

        int IConvertible.ToInt32(IFormatProvider? provider)
        {
            return Convert.ToInt32(m_value);
        }

        uint IConvertible.ToUInt32(IFormatProvider? provider)
        {
            return Convert.ToUInt32(m_value);
        }

        long IConvertible.ToInt64(IFormatProvider? provider)
        {
            return Convert.ToInt64(m_value);
        }

        ulong IConvertible.ToUInt64(IFormatProvider? provider)
        {
            return Convert.ToUInt64(m_value);
        }

        float IConvertible.ToSingle(IFormatProvider? provider)
        {
            return m_value;
        }

        double IConvertible.ToDouble(IFormatProvider? provider)
        {
            return Convert.ToDouble(m_value);
        }

        decimal IConvertible.ToDecimal(IFormatProvider? provider)
        {
            return Convert.ToDecimal(m_value);
        }

        DateTime IConvertible.ToDateTime(IFormatProvider? provider)
        {
            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Single", "DateTime"));
        }

        object IConvertible.ToType(Type type, IFormatProvider? provider)
        {
            return Convert.DefaultToType((IConvertible)this, type, provider);
        }
    }
}
